When you don’t feel good it’s easy to avoid doing the things that require effort, even when you know they are likely to make you feel better. And so you you choose to sit and do nothing.
Perhaps you wallow in self pity over how terrible you feel.
I think it can be helpful to honour this feeling for a short while. It’s perfectly okay not to feel good and not feel like taking action.
However, if you indulge for too long it could become a problem and at the end of the day when you’ve gotten nothing done you’ll only feel worse.
So, sometimes if you don’t feel like it, get up and do something anyway. It doesn’t have to be anything particularly challenging, it could be as simple as going for a walk.
And maybe once you’ve done that, you’ll feel like doing something else.